The applicant of the present application suggested a metal-salen complex as a ferromagnetic metal complex organic molecule. Regarding this metal-salen complex, electron spins of unpaired electron pairs are oriented either up or down relative to their basic skeleton, so that the metal-salen complex itself can exhibit the ferromagnetic property without any help of a magnetic carrier.
Then, the metal-salen complex is magnetically guided by an external magnetic field. So, when the metal-salen complex is applied to a human or an animal, it is guided by the magnetic field outside the body to a region, to which the magnetic field is locally applied, and retained in that region, and can exhibit its originally retained medicinal effect (such as anticancer) locally in the magnetism-applied region (WO2008/001851). As a result, a therapeutic drug made of the metal-salen complex has the ferromagnetic property by itself without using a magnetic carrier as mentioned above, so that it is useful in exhibiting the stable anticancer effect and reducing the occurrence of side effects.
There is also a metal-salen complex described in WO2012/086683 as the above-described metal-salen complex. When the metal-salen complex is used to make it reach an affected site by means of systemic application and remain in the affected site by the magnetic field, a crystal particle diameter of the metal-salen complex is 1 μm or less so that the metal-salen complex can pass through many capillary vessels; and it is preferable that particles whose crystal particle diameter is from 100 nm to 500 nm inclusive should occupy 70% or more of the entire metal-salen complex. If the particle diameter of the metal-salen complex exceeds 1 μm, there is a possibility that the metal-salen complex may not be able to pass through the capillary vessels. If the particle diameter of the metal-salen complex is less than 100 nm, the ferromagnetic property required for magnetic guidance would not be sufficient.